The present invention relates to filters and, more particularly, to edge type filters comprised of a stack of filter discs or elements.
In order to remove solid particles from a flowing gas or liquid wire mesh or sintered filters have sometimes heretofore been used, particularly for the separation of particles smaller than 100 microns. Such filters may have certain advantages when compared to an edge type filter comprised of a stack of filter discs, washers or other sheet elements. In a wire mesh screen, for example, each flow passage through the screen is very short thus minimizing pressure drop through the filter. Additionally, wire mesh screen may be advantageous in maximizing the ratio of open or pore area relative to the solid area of the filter mesh and thus provide a greater filter capacity per unit weight of the structure. However, wire mesh and sintered filters also inherently have certain disadvantages. For example, it is virtually impossible to attain a uniform size of opening of the pores or interstices of a wire mesh or sintered filter; the filters have an inherently low resistance to high pressure differentials; and the filter elements cannot be satisfactorily back-flushed for cleaning and re-use.
Stacked sheet filters, such as that disclosed in Pearson U.S. Pat. No. 3,648,843, overcome many of the disadvantages of wire mesh and sintered filters. However, as compared to wire mesh and sintered filters, stacked sheet filters typically have relatively long flow passages therethrough and, accordingly, induce a relatively high pressure drop. Further, stacked sheet filters have a relatively low ratio of open space to closed space as compared to wire mesh and sintered filters.